The present disclosure relates to a coil module used for wireless charging and an electronic apparatus incorporating the coil module.
In recent years, cellphones having a wireless charging function have come to be marketed. With the recent increase in multifunctionality and screen size and other requirements in or about cellphones, the capacity of battery packs used in cellphones have increased, resulting in increase in full charging time. Shortening of the full charging time would be key to further spread of cellphones. To this end, it is necessary to attend to the quick charging more than in the past.
Quick charging is enabled by running a large current, and resulting heat generation cannot be suppressed sufficiently because of large power that is consumed in a coil. Since heat generated by a coil affects nearby electronic components, running a large current through the coil is associated with difficulties. However, it is possible to increase the current flowing through a coil by radiating the heat generated by the coil to the outside. Among conventional techniques for radiating the heat generated by a coil to the outside is one relating to the coil-incorporated board that is disclosed in JP-A-2008-177516. The coil-incorporated board that is disclosed in JP-A-2008-177516 is provided with plural heat transmission through-conductors which penetrate through a ferrite magnetic layer that encloses a planar coil conductor and a heat radiation conductive layer which is connected to the heat transmission through-conductors. The heat generated by the planar coil conductor is radiated to the outside from the heat radiation conductive layer via the heat transmission through-conductors.
However, the above-described coil-incorporated board disclosed in JP-A-2008-177516 has the following problems. Since the heat transmission through-conductors are formed so as to penetrate through the ferrite magnetic layer, they can be provided only in a limited region (central region) where the planar coil conductor does not exist (i.e., a central region inside the planar coil conductor). Therefore, sufficient heat radiation cannot be attained even with the heat radiation conductive layer and the temperature of the heat radiation conductive layer becomes very high. It is therefore difficult to run a current to the planar coil conductor beyond a somewhat elevated level.